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Fractured Whiteside Ortholoc II knee components
E Swarts1, S J Miller, C V Keogh
1Bioengineering Division, Department of Medical Physics, Royal Perth Hospital, Perth, Western Australia.
The Journal of Arthroplasty
|October 19, 2001
Summary
Failure analysis of Whiteside Ortholoc II total knee arthroplasty components revealed fatigue fractures. Design flaws and material limitations in cast cobalt-chromium-molybdenum alloy contributed to component failure in patients.
Area of Science:
- Orthopedic biomechanics
- Biomaterials science
- Failure analysis
Background:
- Total knee arthroplasty (TKA) components are susceptible to in-service failure.
- Cast cobalt-chromium-molybdenum (Co-Cr-Mo) alloy is commonly used in orthopedic implants.
- Understanding failure mechanisms is crucial for improving implant longevity.
Observation:
- Fracture surfaces consistently indicated fatigue as the failure mechanism.
- Failures were concentrated in areas of high stress, including sharp corners and sintered bead regions.
- Metallurgical analysis revealed variability in grain size, carbides, and hardness, with some showing interfacial voids.
Findings:
- Fatigue failure in cast cobalt-chromium-molybdenum total knee arthroplasty components.
- High stress concentrations at design features and material defects contributed to fractures.
- Patient weight and surgical placement were identified as contributing factors.
Implications:
- Highlights the limitations of cast cobalt-chromium-molybdenum alloy for weight-bearing orthopedic applications.
- Emphasizes the critical role of design, metallurgy, and clinical factors in preventing implant failure.
- Suggests a need for careful material selection and design optimization in total knee arthroplasty.